Unnecessary. What could an average consumer possible do with 18 cores? If not a business powering a server? You could get 10 cores with half the price and that would be still overkill.

My editing system has 12 cores, 64gb ram, and 13tb of internal memory. I am considering building a duplicate system and hooking them together to have 24 cores. It makes a difference when you render 4k in real time.

I have a 6-core i7-5820K CPU that's a bit OC'd as well as an nVidia 980 Ti but 4K video is a bit of a struggle with it. The idea that you could have too much power is nonsense though you do have to have the money for it. My nearly two year old editing PC, which I built from scratch, doesn't handle h.265 very well but the newer CPU's and GPU's appear to be able to work with it natively so even a more modest system using new parts should be a lot better when doing h.265. I suspect that in another year or so even mainstream PC's will do 4K video editing pretty well but then people will be doing 6K and 8K -- it never ends!